75 - 79, 80 Fast Idle Control Valve "FIV" Working on a replacement

[79 Eldorado]

It is evident to me, in an effort to quickly get out a then best state of the art performance, they slapped together a lot of somewhat
revolutionary new stuff and did not do enough testing.  With the new digital designs in sight, no more effort went into fixing these.  Now in
hind sight we are slowly working out all the bugs. 

My ECU work has gotten more complex than a very simple repair, because I also try to head off other potential future failures. 
Bruce Roe

I think you're spot on with the comments... Thankfully the system was used for several years. I cannot image what would have happened if it was 1 year only.

While researching the o-ring for this I contacted a direct manufacturer expert and they recommended Flourosilicone since the most common fuel now has 10% alcohol. I think that material would be good for the fuel injectors seals as well. They are expensive even in quantity but not break the bank expensive. I still plan to do mine and I was thinking of copying the size in one of the kits and buying the Flourosilicone version of the same thing. I will need to remind myself which kit you thought had the correct sizes to reference.

I just went out and tested the prototype on my car with the brass pin I made. I thought I made it conservatively a little long but the pin on my FIV was longer than the ones you sent for reference (I'm sure the physical pin is the same; simply a result of temp and condition of the wax actuator I guess). I also checked the depth of my plunger seat because my car has the "natural" color version and I was measuring the black one you sent. They seem to measure the same (rim to where the pin pushes).

So my preliminary conclusion is it basically acts the same on the car as on the bench. The starting RPM was higher because my pin was shorter. I can also see I need to raise my idle RPM slightly. It was always a bit low but because it wasn't stalling I wasn't touching it. I couldn't believe it didn't stall this morning. It got down to between 460 and 470 RPM but one blip reading was even 435. I need to pull out the books and see what the idle RPM should be. When I started it (giving me ~3sec to run from the key turning to the passenger side and hitting record) was 1510 RPM and it increased very slightly for the first few seconds to 1560-70 before going back down as the pin extended.

Here's the graphical form of the data with the bench current as reference. Bench test shows pin length but I thought it would still be a reference so I added RPM to the secondary axis.

Scott

[bcroe]

Looks like a good run.  Your idle might have been set low before, to compensate
for a FIV that did not fully close. 

Why does the current keep changing after the pin stops moving?  Bruce Roe

[79 Eldorado]

Looks like a good run.  Your idle might have been set low before, to compensate
for a FIV that did not fully close. 

I suspect you are correct. I need to make some progress on a couple of non car related projects before I go back to it

I found the instructions in the "Big red book" 6C-98. It talks about a lock nut but at least on the TB you let me borrow it looks like a supersized version of a Q-Jet idle screw with only a spring and no locking mechanism (does not inspire confidence as easy as it turns). I guess it follows the same logic as the Q-Jet meaning tighter = slower. The book says 600 RPM in drive with vacuum plugged. I will need to get a helper to operate the brakes. I was expecting to see 650 but the Eldorado and Seville are lower; "C" car shows 650. Mine is very low if I'm getting mid 400's in Park.

Why does the current keep changing after the pin stops moving?  Bruce Roe

It needs to maintain the set temperature. So once it achieves the "off" set point the controller just samples every so many seconds to check to see if the temp has dropped below the "restart" temp. When it samples it draws 0.04 Amps (Volt meter showing 0.01 Volts so maybe even lower as I do not have another decimal place). Once the temp drops below the restart you see the full 0.9Amps again but for a shorter time because it's starting from the restart temp and not ambient.

Oh I also checked the resistance of my original and switch open and closed yields almost the same value (26-28Ohms) so one of resistors is bad. That one eventually gets close to closing, even with one resistor bad, because the minimum RPM was getting down to around 540 RPM.

Scott

[79 Eldorado]

I sent my 3D models and drawings out for quote for the housing and cap as injection molded parts. That's the last real part I need. The quote did come back. I'm working through the details. It's not cheap but it seems like the best solution.

I should have an update in less time than it took to post this one. Home projects....

Scott

[79 Eldorado]

I ended up getting some professional 3D printed parts which Mitchell (MaR) was suggesting early in the thread. They were made using an SLS process out of glass filled nylon. The best material was only available in off white instead of black but the parts really look good and we made certain to print them in an orientation which would give the maximum strength in the critical direction. It's still not cheap but at least, unlike the injection mold, the brunt of the cost doesn't need to be spent before the first part is made.

I have one working in my own car now. I'm still tweaking the values based on tolerances and I'm working out the details to allow an abnormal operation shut-off.

The one in my car has the shortest extended length pin (actuator tolerance) and the slowest heating (heating element tolerance). I tried the tallest extended length and the fastest heating last night. It worked as well; RPM came down faster but to the same value. Because my plunger (the thing the FIV pushes against) was pushed farther than it had probably traveled in at least 30 of it's 40 year life the plunger got stuck on the residual carbon build-up. I cleaned it and after cleaning it worked as normal.

Also interesting is there is no wire clip on my car and no witness marks seeming to indicate it's been gone a long time. After studying these as much as I have I would recommend removing the clip and being cautious with FIV replacement if you still have a switch arm. The clip only seems to have the function of keeping the return spring partially compressed during install and removal. If you have a clip you risk the FIV becoming "latched" which is clearly stated as a failure mode in the Cadillac Electronic Fuel Injection "Blue book" and second they can break and you then run the risk of having a clip go through your motor.

Scott

[bcroe]

An actual working replacement is pretty impressive, I wonder if the General
worked much harder to do them?  Bruce Roe

[79 Eldorado]

An actual working replacement is pretty impressive, I wonder if the General
worked much harder to do them?  Bruce Roe

Bruce,
I'm really pretty impressed at what they were able to do over 40 years ago. They had more available resources at their disposal though. I also think a lot of the credit needs to go to Bendix. They should have concentrated a little more on long term durability but the overall system design wasn't so bad when everything was working.

I ran 3 more tests tonight to cover the tolerance range of the actuators. I'm missing one test to fill the max RPM at start-up matrix. I finished the minimum stabilized RPM matrix tonight. I'm still zeroing in on the nominal pin but even with the range I used I would say every combination was probably acceptable; meaning I could have fine tuned with the idle screw on the front of the TB. I think when these are changed that adjustment will be necessary anyway. I also measured the total turns possible on the TB idle screw. From completely removed to fully seated it was 21.5 turns. I didn't check the total usable range but it's likely around 8 (fully closed to passage fully open).

The controller I'm using has some built in precautions for abnormal behavior. The three I have now are missing one of those available control schemes which I want to add. I will also adjust the resistance of the heating element some based on the necessary manufacturing tolerance and equalization time. Once I have the updated controllers and heating element I do plan to send you one to try.

Scott

[79 Eldorado]

My car has put-up with a LOT of testing. I’ve finally decided on what I feel are the final adjustments. I’m ordering 3 more of the key electronics, in what I believe is the final configuration, for a final verification before committing to a larger quantity to get the price down. The sample quantity prices are painful.

Other than testing I created a calculator which is able to estimate the heat-up time for a given resistance. I also used the CAD model, of the FIV assembly and the TB key parameters, to make a spreadsheet based math model for determining the best target for the actuator motion.  The math model makes the position where the plunger overlap, relative to the actuator motion, more obvious. I can vary parameters and immediately see the bypass gap or overlap value. To explain the car RPM should plateau before the controller off command. That means there is overlap beyond the plunger initial close position, linear position when bypass equals zero, and the final plunger position. That’s important because it allows tolerance and it adds stability during control. I learned during this project that the tolerance of the actuator stroke is based on an internationally accepted tolerance; 10% of the total stroke.

My original, with one bad resistor, seemed tolerable at the time but it’s so much better now.

Scott

[79 Eldorado]

One of the forum members was having an issue with his '76 Eldorado convertible. Very nice dark brown color with white interior. He inspired me to write-up a removal / installation instruction sheet. It's a draft which I intend to add photos to but once it's done I will post it on the forum.

His car now has "proto3" with a custom length pin installed and working. He even took some photos while going through the procedure ( a couple are attached). The plan is to swap proto3 with one of the final versions once they are done. He was thinking about parking it for the season. I've been in the same situation where something cuts the season short and it's not a good feeling.

Scott

[bcroe]

Very impressive, keep us informed on the trial.  Some of us do not stop
driving 70s cars in winter.  Bruce Roe

[79 Eldorado]

Bruce,
The member found me through you. Following the repair he is getting a lot more seat-time and he now feels safe driving his car. I think he will post an update directly.

As I posted the update the fact that you continue to drive your car, as some of us store them, was certainly running through my mind. I wanted to send you one of the three prototypes. My primary reluctance in sending one of my prototypes to you was my rather crude actuator pin. It works but I don't have a lathe so to test different lengths I used my drill press to turn down the closest diameter I could find to the required 4.6mm. I have a crude pin in my car but if I drop it while working over the TB I have only myself to blame.

For "proto3" I sent out I cut down the only original pin which was long enough to be the ideal length. I have 3 samples but the other two were ordered with intentionally short pins thinking I could thread them and use an adjustable machine screw with a lock nut. The pin material is 304 stainless and I anticipated needing "flats", to grasp it while threading, so the diameter I could tap was really small. I thought I could do it but the tap was small and the material was so hard I broke my tap after the third or fourth thread. Anyway I placed a larger "production" order for the wax actuators and I am within a couple of business days away from placing the order for the key internal electronic parts.

There are a couple of other parts I need but those parts are either the same or very similar to the prototypes. So other than the actuators and electronics I currently have enough parts to make 7 more assemblies. I think the timing to replenish the items I have 7 sets of will be similar to the actuators and electronics.

I'm anticipating having these available sometime in October. I don't think the timeline will slip.

Scott

[ctbrooklyn]

Hi all.

I am the member who was fortunate enough to try out Scott's newly minted FIV piece. A little back story on my 76 Eldo...

It's a low mileage car at 62k miles. It gets driven only between late May and mid October, after which it is put away for the winter. I'm located in New England, so for reasons of salt and the fact that I winter in Florida, the car is parked in my well-ventilated, elevated barn and the battery is then moved to a tender in my basement. All told, I normally drive the convertible about 1,200 miles per summer season.

This year, upon first starting the car in late May, I noticed it would not idle down while in DRIVE. The motor seemed to be constantly revved at very high RPMs, and required heavy braking to keep her under control in the hills where I live. It simply was not safe to drive her and distance. Because of this, I drove it very little, and then only two or three miles to keep her exercised a bit.

Reaching out to Bruce Roe, he offered great advice and also mentioned Scott and his quest for a better FIV. The rest, really, is history. I am by no means a mechanic, but I can generally find my way under the hood of a car. Having very few auto repair shops here where I live, and knowing the rarity of the fuel injection system on these cars, I began my quest to fix the car mostly out of necessity. Otherwise, I'd not be able to enjoy Vivienne on those great summer days.

This FIV manufactured by Scott is the real deal. I was able to replace mine in well under 30 minutes. The only issue after replacing the part is then fiddling with the idle screw, which takes all of 60 seconds each time. This was a hit or miss situation, as I adjusted it over three days until I felt the car was right where she ran at her best. All told, the replacement of the FIV and idle screw finessing was very easy. I was apprehensive (to say the least), but Scott's directions and his new FIV make it an easy proposition. I feel very comfortable (and happy) driving the car. Monday I took her out in nice weather. I drove her 23 miles as I ran several errands. Stopping three times along the way, where she sat for five to ten minutes each time, she started right up and drove as one would hope! No more high idle and reining her in as I drove.

If the FIV is the problem, then Scott's piece is the answer. Feeling comfortable as I drive with the top down, Simon & Garfunkel in the 8-track, that's what it's all about for me.

I'm happy to answer any questions should anyone have any. Thanks so much, Scott!

Joel

[79 Eldorado]

Thanks for posting Joel.

The actuators arrived a week ago Monday (see photo attached). I replaced the actuator in one of my prototypes with one of the new ones. That sample was tested on my bench test, using the extra TB Bruce supplied, and it iworked as intended.

The last electronics part is later than I expected. All of the items I initially saw as difficult have been sorted but I've been working with the supplier to get the best wire available for the assembly. My first selection from their current supplier was not something stocked and thus there was a very large minimum order quantity. I did find an alternative supplier for the wire so hopefully things will start moving again more quickly.

Scott

[79 Eldorado]

The final part I was waiting for should arrive tomorrow the 9th of December so I should have another update soon. I want to try everything out with the parts I have before I order more of the custom brass sleeves I've been using.

Scott

[79 Eldorado]

The assembly with all of the final parts is finally done and ready to confirm! I'm including a photo of that first part. It's pictured still in a quick-clamp while the adhesive cures. The thing at the bottom of the FIV is an interface I 3D printed to allow the 2 halves of the FIV to be clamped with even pressure over the surface; needed to avoid the pin/actuator and distribute the load over both "feet".

The local company making the brass heat sink had some time on a machine so instead of modifying one of my prototypes I decided to wait until they had the final version. That was this morning. I approved the design today so I should have more heat sinks coming soon. I only have 7 housings left but I spoke to the supplier today to get more.

I'm pretty excited with the way the first one came out. I will wait the full 24 hours, full cure time for the adhesive, before testing it. Even though the cap sees no load I want to let it fully cure.

Scott

[bcroe]

Lots of work there, guess it will be a while before trials are complete.

Bruce Roe

[79 Eldorado]

Bruce,
I've done so many tests, taken so many measurements, have so much data and have the TB area around the FIV modeled with an interactive workbook which tells me the gap/overlap. I should really just need to test it on my bench test and check the numbers against my existing data. I'll either do it tomorrow or Wednesday.

I patterned the resistance using one of the prototypes. I've already tested/verified the wax actuator and pin length. Those items are key. I did change the sleeve slightly for some added internal clearance but it was and still is a pretty significant heat sink. The final, hopefully final, design is modeled after the part I have in my car. The part in Joel's car is faster acting than what the final values targeted. The part Joel has still worked pretty well once I adjusted the pin length. There seems to be a fair amount of room for variation to have an acceptable part. The standard tolerance for the heating element was +/-10% which I think would have been ok but I was a little concerned and the supplier agreed to keep the parts I purchased within +/-6%. Joel's part was around 20% lower resistance than mine.

Scott

[79 Eldorado]

The first part is bench tested and it worked as expected. I'm attaching a portion of the test data summary. The first line is my "Proto1" and the second for this first sample.

If you take the gap at the beginning of the test and subtract the "gap" (negative because it's now overlap) at the end of the test you can get the total pin travel.

Scott

[79 Eldorado]

I took some photos after removal from the clamp and after testing.... See attached.

Scott

[bcroe]

I took some photos after removal from the clamp
and after testing.... See attached.  Scott 

That certainly does look professional and expensive.  I suppose you are now into
calibrating things like the time delay, rod movement, and power usage?  There is
plenty of 12V power available from the fuel pump circuit, I suppose the original
used that delicate switch to keep it from getting too hot.  Bruce Roe